The present disclosure relates generally to wireless communications technologies. More particularly, the present disclosure relates to enabling coexistence of high-density and low-density transmissions.
Wireless capability allows a variety of devices to communicate with each other adding to the mobility of users. A computing device, such as a Personal Computer (PC), may be used with various peripherals that are not wired together, but rather communicate using wireless communications, such as Wireless Local Area Network (WLAN) type protocols.
The density of the future distributed systems such as WiFi™ keeps growing. One very relevant example is that Intel is trying to ramp up density of wireless displays (WiDi). Wireless display (WiDi) is a technology in which image information, such as video information and audio information, on a computer display/screen is captured and encoded, and is then wirelessly transmitted to an adapter. For example, the video information and audio information may be wirelessly transmitted through WiFi™, which is a superset of the standards of IEEE 802.11 for a WLAN protocols. The video data is then decoded and displayed on another screen, such as a screen on a high definition television (HDTV) and the audio may be decoded and sounded through speakers for the HDTV. The quality of the video and audio expressed by the HDTV is dependent upon the throughput of the wireless channel for transmitting the encoded video and audio data. The throughput of the wireless channel is dependent upon channel conditions, such as the signal to noise ratio (SNR), which may detrimentally change to adversely affect video quality on the display screen and/or the audio quality sounded by the speakers.
It is well-known that using excessive power, e.g. 17 dBm (decibels relative to one milliwatt), is unnecessary and actually lowers system performance significantly due to interference with reception of parallel transmissions. For example, a 17 dBm plus 3 dBi (decibel isotropic) antenna has an interference radius of about 40 to 50 meters, while zero dBm is enough to provide 30 dB SNR at a distance of five meters. Shrinking from full power for transmissions to a power level that is necessary could achieve five times more transmissions.
Yet, not many devices are lowering power due to the fact that the act only benefits other devices and not necessarily the devices that actually lower the power for transmissions. Lowering the power for transmission may even interfere with ability of a receiving device to receive the transmission when there are legacy devices nearby. The receiving device may have difficulty receiving the lower power transmission because of the asymmetric interference footprint between the high power or excessive power transmissions from legacy devices and the low power transmissions. The low power link established for the low power transmissions may not be able reach the legacy devices but the high power transmissions from a high power link can reach the low power devices and destroy the well-known CSMA-based RTS/CTS/DATA/ACK handshake for preventing hidden nodes.